Table of contents

1. A Review of General Chemistry5h 5m
2. Molecular Representations1h 14m
3. Acids and Bases2h 46m
4. Alkanes and Cycloalkanes4h 17m
5. Chirality3h 39m
6. Thermodynamics and Kinetics1h 22m
7. Substitution Reactions1h 48m
8. Elimination Reactions2h 30m
9. Alkenes and Alkynes2h 9m
10. Addition Reactions3h 19m
11. Radical Reactions1h 58m
12. Alcohols, Ethers, Epoxides and Thiols2h 42m
13. Alcohols and Carbonyl Compounds2h 17m
14. Synthetic Techniques1h 26m
15. Analytical Techniques:IR, NMR, Mass Spect7h 3m
16. Conjugated Systems6h 13m
17. Ultraviolet Spectroscopy51m
18. Aromaticity2h 34m
19. Reactions of Aromatics: EAS and Beyond5h 1m
20. Phenols55m
21. Aldehydes and Ketones: Nucleophilic Addition4h 56m
22. Carboxylic Acid Derivatives: NAS2h 51m
23. The Chemistry of Thioesters, Phophate Ester and Phosphate Anhydrides1h 10m
24. Enolate Chemistry: Reactions at the Alpha-Carbon1h 53m
25. Condensation Chemistry2h 9m
26. Amines1h 43m
27. Heterocycles2h 0m
28. Carbohydrates5h 53m
29. Amino Acids4h 20m
30. Peptides and Proteins2h 42m
31. Catalysis in Organic Reactions1h 30m
32. Lipids 2h 50m
33. The Organic Chemistry of Metabolic Pathways2h 52m
34. Nucleic Acids1h 32m
35. Transition Metals6h 14m
36. Synthetic Polymers1h 49m

10. Addition Reactions

Hydrohalogenation

Organic Chemistry

10. Addition Reactions

Hydrohalogenation

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1:52 minutes

Problem 33

Textbook Question

Would you expect but-2-ene or 2-methylbut-2-ene to react more quickly with HBr?

Verified step by step guidance

Identify the type of reaction: Both but-2-ene and 2-methylbut-2-ene will undergo an electrophilic addition reaction with HBr, where the alkene reacts with the hydrogen bromide to form a bromoalkane.

Consider the stability of the carbocation intermediate: In electrophilic addition reactions, the alkene forms a carbocation intermediate. The stability of this carbocation is crucial in determining the rate of the reaction.

Analyze the structure of but-2-ene: When but-2-ene reacts with HBr, it forms a secondary carbocation. Secondary carbocations are relatively stable, but not as stable as tertiary carbocations.

Analyze the structure of 2-methylbut-2-ene: When 2-methylbut-2-ene reacts with HBr, it forms a tertiary carbocation due to the presence of the methyl group, which provides additional stabilization through hyperconjugation and inductive effects.

Compare the stability of the carbocations: Tertiary carbocations are more stable than secondary carbocations. Therefore, 2-methylbut-2-ene, which forms a tertiary carbocation, is expected to react more quickly with HBr compared to but-2-ene, which forms a secondary carbocation.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Markovnikov's Rule

Markovnikov's Rule states that in the addition of HX (where X is a halogen) to an alkene, the hydrogen atom will attach to the carbon with more hydrogen atoms, and the halogen will attach to the carbon with fewer hydrogen atoms. This rule helps predict the major product of the reaction based on the stability of the carbocation intermediate.

Carbocation Stability

Carbocation stability is crucial in determining the rate of alkene reactions with HX. Tertiary carbocations are more stable than secondary or primary ones due to hyperconjugation and inductive effects. In the reaction of alkenes with HBr, the formation of a more stable carbocation intermediate leads to a faster reaction rate.

Steric Hindrance

Steric hindrance refers to the resistance encountered by a chemical reaction due to the size of groups within a molecule. In alkenes, bulky substituents can slow down reactions by impeding the approach of reactants. Comparing but-2-ene and 2-methylbut-2-ene, the latter has more steric hindrance due to the methyl group, potentially affecting its reactivity with HBr.

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Related Practice

Textbook Question

What is the major product of each of the following reactions, assuming that one equivalent of each reagent is used in each reaction?

Textbook Question

Predict the product(s) of each of the following reactions. If you expect a racemic mixture, draw both enantiomers.

(c)

Textbook Question

Suggest an alkene that, upon reaction with the appropriate hydrohalic acid, will produce only the alkyl halide shown. [Ignore stereochemistry.]

(b)

Textbook Question

What is the expected product for the reaction of each of the following alkenes with (i) HBr and (ii) HCl?

(d)

Textbook Question

If you react carvone with a single equivalent of HBr, only one product is produced, even though carvone has two carbon–carbon double bonds. Explain this observation.

Textbook Question

The reaction of (E)-3-chlorohex-3-ene with HCl results in the selective formation of 3,3-dichlorohexane instead of 3,4-dichlorohexane. Explain this result.

Textbook Question

Predict the product(s) that would result when the alkenes shown here are allowed to react under the following conditions: (i) HBr;

(b)

Textbook Question

Predict the product(s) that would result when the alkenes shown here are allowed to react under the following conditions:(ii) HCl;

(b)

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